tailieunhanh - Báo cáo khoa học: The noncatalytic C-terminus of AtPOLK Y-family DNA polymerase affects synthesis fidelity, mismatch extension and translesion replication

Cell survival depends not only on the ability to repair damaged DNA but also on the capability to perform DNA replication on unrepaired or imperfect templates. Crucial to this process are specialized DNA polym-erases belonging to the Y family. These enzymes share a similar catalytic fold in their N-terminal region, and most of them have a less-well-con-served C-terminus which is not required for catalytic activity. | ễFEBS Journal The noncatalytic C-terminus of AtPOLK Y-family DNA polymerase affects synthesis fidelity mismatch extension and translesion replication Maria Victoria Garcia-Ortiz Teresa Roldan-Arjona and Rafael R. Ariza Departamento de Genetica Universidad de Cordoba Spain Keywords Arabidopsis thaliana base-pair mismatch DNA damage DNA replication translesion DNA synthesis Correspondence R. R. Ariza Departamento de Genetica Edificio Gregor Mendel Campus de Rabanales s n Universidad de Cordoba 14071-Cordoba Spain Fax 34 957 212 072 Tel 34 957 218 979 E-mail ge1roarr@ Received 10 April2007 accepted 4 May 2007 doi Cell survival depends not only on the ability to repair damaged DNA but also on the capability to perform DNA replication on unrepaired or imperfect templates. Crucial to this process are specialized DNA polymerases belonging to the Y family. These enzymes share a similar catalytic fold in their N-terminal region and most of them have a less-well-conserved C-terminus which is not required for catalytic activity. Although this region is essential for appropriate localization and recruitment in vivo its precise role during DNA synthesis remains unclear. Here we have compared the catalytic properties of AtPOLK an Arabidopsis orthologue of mammalian pol K and a truncated version lacking 193 amino acids from its C-terminus. We found that C-terminally truncated AtPOLK is a high-efficiency mutant protein the DNA-binding capacity of which is not affected but it has higher catalytic efficiency and fidelity than the full-length enzyme. The truncated protein shows increased propensity to extend mispaired primer termini through misalignment and enhanced error-free bypass activity on DNA templates containing 7 8-di-hydro-8-oxoGuanine. These results suggest that in addition to facilitating recruitment to the replication fork the C-terminus of Y-family DNA polymerases may also play a role in the kinetic control of their enzymatic .